In the manufacture of many articles including transportation vehicles such as automobiles including cars, trucks, busses, caravans and the like, aircraft and railroad vehicles it is necessary to seal a joint between two surfaces lying adjacent one another often to seal surfaces in generally parallel planes, for example surfaces (such as panels) that are butted together or overlap one another. U.S. Pat. No. 4,719,689 illustrates such a technique. The invention is applicable to such sealing and is particularly useful in the formation of a hem flange, such as may be found on a vehicle body. The invention also relates to a method of sealing a joint between two adjacent surfaces.
A hem flange between two panels is formed by turning an extended edge portion of one panel back over an edge portion of a second panel and sealing the edge of the second panel within the extended edge portion of the first panel. Hem flanges can be found in various locations in vehicle bodies where two panels are joined together, for example on doors, boot lids and bonnets. A vehicle door, for example, may be formed from an inner panel and an outer panel joined together along their outer edges by a hem flange which is formed by turning the extended edge portion of the outer panel back over the edge portion of the inner panel to form an overlap joint, and crimping the edges together. A seal is then needed between the edge of the outer panel and the adjacent surface of the inner panel, to keep moisture out of the space between the panels and prevent corrosion. Traditionally two or three different materials have been used to provide the join, an adhesive, a paintable covering layer and perhaps a protective layer such as wax. This invention allows the joint to be produced employing fewer materials.
If a vehicle door is damaged, it can sometimes be repaired by replacing only the outer panel but, if that is done, it is clearly desirable (from the point of view of the vehicle owner) that the repaired door should match the original as closely as possible not only in quality but also in appearance. In practice, one of the most difficult parts of the repair job is to seal the hem flange effectively and in such a way that it closely resembles the seal on the original door, which would generally have been formed by an automated process.
The formation of a hem flange is described in PCT publication WO 97/01052 and in JP 63-202680 and sealing materials useful for the formation of a hem flange seal are described in WO 03/022953.
In these techniques the joint between the two metal pieces is formed by first forming a U or C shaped cup at the end of one of the metal pieces, inserting the edge of the second metal piece into the U or C shaped cup and providing a sealant material within the remaining space of the U or C shaped cup which bonds the two metal pieces together. The sealant material may be heat activatable so that its adhesive properties are developed at temperatures employed during manufacture such as, for example, paint bake ovens or anti-corrosion (e-coat) bake ovens. The sealant materials that are used are often foamable. In many operations it is necessary to provide a desired surface finish and weatherproofing over the joint. For example in many instances such as a vehicle hem flange the joint must have a good esthetic appearance, be damp and moisture resistant so that it does not become a site for rust or other forms of corrosion. It is therefore common practice to provide a finishing material such as a paintable wax over the sealant to provide protection and the desired surface finish.
In PCT publication WO 03/022953 we describe the production of a hem flange which can serve to reduce and/or eliminate the step of pre-crimping the selected panels during the manufacturing process. The method comprises of: providing a structural member having two substrates forming a space to be joined; placing a structural material comprising, in parts by weight, less than about twenty percent (<20%) ethylene copolymer, less than about forty percent (<40%) epoxy, less than about thirty percent (<30%) epoxy-based resin, less than about two percent (<2%) blowing agent and from about one percent (1%) to about five percent (5%) curing agent, (and optionally includes any of the following components; less than about two percent (<2%) curing agent accelerator, from about twenty-five percent (25%) to fifty-five percent (55%) filler, and less than about one percent (>1%) of colouring agent. The structural material is placed in proximity of the space to be joined, the structural material is then exposed to heat or other energy source causing the structural material to flow, fill, and cure in the defined area or space to be joined thereby providing post-cure structural integrity and rigidity to the selected are a or space of the land, marine, or aerospace vehicle.
However the use of this method still requires a finishing material in order to avoid corrosion and enable painting. Furthermore, the production of joints in this manner is therefore time consuming and also can result in joints of variable quality having irregularities and unsightly sections. The present invention provides a solution to these problems.